#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<unistd.h>
#include<sys/types.h>
#include<sys/wait.h>
#include<cstring>
#include<unordered_map>

#define COMMAND_SIZE 1024
#define FORMAT "[%s@%s %s]# "

//全局数据

//1.命令行参数表
#define MAXARGC 128
char *g_argv[MAXARGC];
int g_argc = 0;

//2.环境变量表
#define MAX_ENV 100
char *g_env[MAX_ENV];
int g_envs = 0;

//3.别名映射表
std::unordered_map<std::string, std::string> alias_list;

//for test
char cwd[1020];
char cwdenv[1024];

//last exit code
int lastcode = 0;

const char *GetUserName()
{
    const char *name = getenv("USER");
    return name == NULL ? "None" : name;
}

const char *GetHostName()
{
    const char *hostname = getenv("HOSTNAME");
    return hostname == NULL ? "None" : hostname;
}

const char *GetPwd()
{
    //const char *pwd = getenv("PWD");
    const char *pwd = getcwd(cwd, sizeof(cwd));//// 获取当前工作目录
    if(pwd != NULL)
    {
        snprintf(cwdenv, sizeof(cwdenv), "PWD=%s", cwd);// 生成PWD=xxx格式
        putenv(cwdenv);// 注册为环境变量
    }
    return pwd == NULL ? "None" : pwd;
}

const char *GetHome()
{
    const char *home = getenv("HOME");
    return home == NULL ? "" : home;
}

void InitEnv()
{
    extern char **environ;
    memset(g_env, 0, sizeof(g_env));
    g_envs = 0;
    //从配置文件来
    //1.获取环境变量
    for(int i = 0; environ[i]; i++)
    {
        //1.1申请空间 因为是指针数组，给指针申请空间
        g_env[i] = (char*)malloc(strlen(environ[i])+1);
        strcpy(g_env[i], environ[i]);
        g_envs++;
    }
    g_env[g_envs++] = (char*)"HAHA = for_test";//for test
    g_env[g_envs] = NULL;

    //2.导成环境变量
    for(int i = 0; g_env[i]; i++)
    {
        putenv(g_env[i]);
    }
    environ = g_env;
}

//command
bool Cd()
{
    //cd argc = 1
    if(g_argc == 1)
    {
        std::string home = GetHome();
        if(home.empty()) return true;
        chdir(home.c_str());
    }
    else
    {
        std::string where = g_argv[1];
        //cd - / cd ~
        if(where == "-")
        {
            //Todu
        }
        else if(where == "~")
        {
            //Tpdu
        }
        else
        {
            chdir(where.c_str());
        }
    }
        return true;
}

void Echo()
{
    if(g_argc == 2)
    {
        //echo "hello world"
        //echo $?
        //echo $PAtH
        std::string opt = g_argv[1];
        if(opt == "$?")
        {
            std::cout << lastcode << std:: endl;
            lastcode  = 0;
        }
        else if(opt[0] == '$')
        {
            std::string env_name = opt.substr(1);
            const char* env_value = getenv(env_name.c_str());
            if(env_value)
                std:: cout << env_value << std:: endl;
        
        }
        else
        {
            std::cout << opt << std:: endl;
        }
    }
}

// a/b/c
std::string DirName(const char *pwd)
{
#define SLASH "/"
    std::string dir = pwd;
    if(dir == SLASH) return SLASH;
    auto pos = dir.rfind(SLASH);
    if(pos == std::string::npos) return "BUG?";
    return dir.substr(pos+1);
}


void MakeCommandLine(char cmd_prompt[], int size)
{
    char hostname[256] = {0};
    gethostname(hostname, sizeof(hostname)); // 直接在这获取主机名
    snprintf(cmd_prompt, size, FORMAT, GetUserName(), hostname, GetPwd());

}

void PrintCommandPrompt()
{
    char prompt[COMMAND_SIZE];
    MakeCommandLine(prompt, sizeof(prompt));
    printf("%s", prompt);
    fflush(stdout);
}

bool GetCommandLine(char *out, int size)
{
    char *c = fgets(out, size, stdin);
    if(c == NULL) return false;
    out[strlen(out) - 1] = 0;//清理\n
    if(strlen(out) == 0) return false;
    return true;

}

bool CommandParse(char* commandline)
{
#define SEP " "
    g_argc = 0;
    g_argv[g_argc++] = strtok(commandline, SEP);
    while((bool)(g_argv[g_argc++] = strtok(nullptr, SEP)));
    g_argc--;
    return g_argc > 0 ? true:false;
}

void PrintArgv()
{
    for(int i = 0; g_argv[i]; i++)
    {
        printf("argv[%d]:%s\n", i, g_argv[i]);
    }
    printf("argc: %d\n", g_argc);
}

bool CheckAndExecBuiltin()
{
    std::string cmd = g_argv[0];
    if(cmd == "cd")
    {
        Cd();
        return true;
    }
    else if(cmd == "echo")
    {
        Echo();
        return true;
    }
    else if(cmd == "export")
    {
    }
    else if(cmd == "alias")
    {
       // std::string nickname = g_argv[1];
       // alias_list.insert(k, v);
    }

    return false;
}

int Execute()
{
    pid_t id = fork();
    if(id == 0)
    {
        //child
        execvp(g_argv[0], g_argv);
        exit(1);
    }
    int status = 0;
    // father
    pid_t rid = waitpid(id, &status, 0);
    if(rid > 0)
    {
        lastcode = WEXITSTATUS(status);
    }
    return 0;
}

int main()
{
    // shell 启动的时候，从系统中获取环境变量
    // 我们的环境变量信息应该从父shell统一来
    InitEnv();

    while(true)
    {
        // 1. 输出命令行提示符
        PrintCommandPrompt();

        // 2. 获取用户输入的命令
        char commandline[COMMAND_SIZE];
        if(!GetCommandLine(commandline, sizeof(commandline)))
            continue;

        // 3. 命令行分析 "ls -a -l" -> "ls" "-a" "-l"
        if(!CommandParse(commandline))
            continue;
        //PrintArgv();

        // 检测别名
        // 4. 检测并处理内键命令
        if(CheckAndExecBuiltin())
            continue;

        // 5. 执行命令
        Execute();
    }
    //cleanup();
    return 0;
}

































